Method for controlling a transmission of a motor vehicle

ABSTRACT

A method for controlling a motor vehicle transmission ( 11 ) is disclosed in which a sensor ( 18 ) used to produce an indication of position of a selector ( 17 ) is calibrated such that positioning the selector ( 17 ) at a peak force feedback position produced by a peak and trough force feedback mechanism ( 24 ) connected to the selector ( 17 ) will always result in the selection of a drive mode of the transmission ( 11 ).

The present invention relates to a method for controlling a transmissionfor a motor vehicle and in particular to a method for controlling theoperation of multi-stable shift-by wire selector control system of anautomatic or semi-automatic vehicle transmission.

It is known from, for example, GB-A-2420833 to provide a shift-by-wireselector having multi-stable positions, each operating a mode of theautomatic transmission, i.e. Park, Reverse, Neutral, Drive. The selectorincludes sensor means for sensing the position of the selector andgenerating selector signals to a transmission control unit whichtransmits control signal to the vehicle transmission and an indexingmechanism for maintaining the selector in each of its multi-stablepositions. The indexing means has a detent plate having notches forcooperation with a mechanical detent having a configurable force.

Although such a selector has been proven effective, it has been foundthat it is possible for the selector to be left between two positions,e.g. between a Park position and/or a Neutral position. When thishappens, the selector might be able to be moved by a subsequentvibration, shock or even unintentionally by a person and engaged a drivemode (Drive, Reverse) of the automatic transmission even if the selectoris left in Park position as the selector cannot be locked by a lockmechanism which can only be engaged when the selector is in a nominalPark position or Neutral position and thus might cause an unsafe vehiclecondition.

It is an object of the present invention to provide an improved controlsystem which overcomes or alleviates the above problem.

According to a first aspect of the invention there is provided a methodfor controlling a transmission of a motor vehicle having a number ofoperating modes including at least one non-drive mode and at least onedrive mode and a multi-stable selector for operation by a driver of thevehicle to select a respective one of the operating modes of thetransmission, the multi-stable selector including a mechanism providinga number of stable positions corresponding to the operating modes and apeak and trough force feedback to the driver so as to enable the driverto perceive the transition from one stable position to another and atleast one sensor to sense the position of the selector and supply asignal to an electronic controller indicative of a required operatingmode wherein the method comprises calibrating the output from the atleast one sensor such that, when the selector is located at any one ofthe peak force feedback positions, the signal from the at least onesensor always results in the selection by the electronic controller of adrive mode.

The transmission may have two non-drive modes in the form of a park modeand a Neutral mode and two drive modes in the form of a reverse mode anda forward mode.

The multi-stable selector may be operable to reversibly select theoperating modes in the sequence park, reverse, neutral and drive.

The transmission may further comprise a third drive mode in the form ofa sport mode. In which case, the multi-stable selector is operable toreversibly select the operating modes in the sequence park, reverse,neutral, drive and sport.

The electronic controller may comprise an electronic transmissionselector operably connected to a transmission control unit, theelectronic transmission selector may be arranged to receive the signalfrom the at least one sensor and command the transmission control unitto select a desired operating mode.

The method may further comprise dividing the output range of the atleast one sensor into a number of bands having upper and lower limitscorresponding to the various operating modes and calibrating the outputfrom the at least one sensor further comprises arranging the bands suchthat, when the selector is located at any one of the peak force feedbackpositions, the magnitude of signal output from the at least one sensorfalls within one of the drive mode bands.

The upper and lower limits of each band may be higher when the selectoris moved in one direction than they are when the selector is moved in anopposite direction.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral and neutral to drive thanthey are when the selector is moved from one of drive to neutral,neutral to reverse and reverse to park.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral, neutral to drive and driveto sport than they are when the selector is moved from one of sport todrive, drive to neutral, neutral to reverse and reverse to park.

According to a second aspect of the invention there is provided anapparatus for controlling a motor vehicle transmission having a numberof operating modes including at least one non-drive mode and at leastone drive mode, the apparatus comprising a multi-stable selector foroperation by a driver of the vehicle to select a respective one of theoperating modes of the transmission, at least one sensor for sensing theposition of the selector and an electronic controller to receive anoutput signal from the at least one sensor and select an operating modeof the transmission based upon the received signal wherein themulti-stable selector includes a mechanism providing a number of stablepositions corresponding to the operating modes and a peak and troughforce feedback to the driver so as to enable the driver to perceive thetransition from one stable position to another and the electroniccontroller is operable to receive the output from the at least onesensor and calibrate the sensor output such that, when the selector islocated at any one of the peak force feedback positions, a drive mode ofthe transmission is always selected.

The transmission may have two non-drive modes in the form of a park modeand a Neutral mode and two drive modes in the form of a reverse mode anda forward mode.

The multi-stable selector may be operable to reversibly select theoperating modes in the sequence park, reverse, neutral and drive.

The transmission may further comprise a third drive mode in the form ofa sport mode. In which case, the multi-stable selector may be operableto reversibly select the operating modes in the sequence park, reverse,neutral, drive and sport.

The electronic controller may be further operable to divide the outputrange of the at least one sensor into a number of bands having upper andlower limits corresponding to the various operating modes and arrangethe bands such that, when the selector is located at any one of the peakforce feedback positions, the magnitude of signal output from the atleast one sensor falls within one of the drive mode bands.

The upper and lower limits of each band may be higher when the selectoris moved in one direction than they are when the selector is moved in anopposite direction.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral and neutral to drive thanthey are when the selector is moved from one of drive to neutral,neutral to reverse and reverse to park.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral, neutral to drive and driveto sport than they are when the selector is moved from one of sport todrive, drive to neutral, neutral to reverse and reverse to park.

The electronic controller may comprise an electronic transmissionselector operably connected to a transmission control unit and theelectronic transmission selector may be operable to receive the outputfrom the at least one sensor and calibrate the sensor output such that,when the selector is located at any one of the peak force feedbackpositions, the electronic transmission selector is arranged to commandthe transmission control unit to select a drive operating mode.

The electronic transmission selector may be further operable to dividethe output range of the at least one sensor into a number of bandshaving upper and lower limits corresponding to the various operatingmodes and arrange the bands such that, when the selector is located atany one of the peak force feedback positions, the magnitude of signaloutput from the at least one sensor falls within one of the drive modebands.

The upper and lower limits of each band may be higher when the selectoris moved in one direction than they are when the selector is moved in anopposite direction.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral and neutral to drive thanthey are when the selector is moved from one of drive to neutral,neutral to reverse and reverse to park.

The upper and lower limits may be higher when the selector is moved fromone of park to reverse, reverse to neutral, neutral to drive and driveto sport than they are when the selector is moved from one of sport todrive, drive to neutral, neutral to reverse and reverse to park.

According to a third aspect of the invention there is provided a motorvehicle having an apparatus for controlling a motor vehicle transmissionhaving a number of operating modes including at least one non-drive modeand at least one drive mode constructed in accordance with said secondaspect of the invention.

The invention will now be described by way of example with reference tothe accompanying drawings of which:—

FIG. 1 is a schematic representation of the principal electricalsubsystems of a motor vehicle provided with a multi-stable shift-by-wirecontrol selector system in accordance with the present invention;

FIG. 2 is a schematic representation of the means used to process theoutput from a sensor means used to sense the position of a gearselector;

FIG. 3 is a schematic diagram showing further detail of the selectorsystem shown in FIG. 1;

FIGS. 4A to 4D are sketches of various sensor arrangements;

FIG. 5 is a graph illustrating the profile perceived by a driver whenmanipulating the selector in its different position and the sensorcalibration used in a prior art selector system;

FIG. 6 is a graph similar to FIG. 5 but showing sensor calibration of aselector system according to a first embodiment of the invention;

FIG. 7 is a graph illustrating the profile perceived by a driver whenmanipulating the selector in its different position and the sensorcalibration used in a second embodiment of the invention in whichhysteresis is provided between each of the various selector positions;

FIG. 8 is a flow chart showing a method according to the firstembodiment of the invention; and

FIG. 9 is a flow chart showing a method according to the secondembodiment of the invention.

With reference to FIGS. 1 to 4 there is shown an electrical architectureof a motor vehicle 1 including an engine 10, an automatic gearbox ortransmission 11 and a multi-stable selector system 12.

The transmission 11 is controlled by a transmission control unit (TCU)16 which includes sensors arranged to detect the position of thetransmission. The TCU 16 is electrically connected by a CAN 21 and abackup CAN 22 to an Electronic Transmission Selector (ETS) 20 which iselectrically connected to the selector system 12. The CAN 21 is used tointerconnect the electronic sub-systems of the vehicle 1 together sothat they can communicate as required with one another.

The selector system 12 is provided in the passenger compartment forenabling the selection of operating modes in the transmission, e.g. Park(P), Reverse (R), Neutral (N), Drive (D) and Sport (S).

The selector system 12 comprises a selector, which in this example is arotary selector 17 which can be grasped by the driver to select theoperating mode and sensor means in the form of one or more positionsensors 18. In this case, see FIG. 4A, the position sensor is an angularsensor 18, to detect the position of the rotary selector 17 (indicatedas ‘A’ on FIG. 4A) as well as the direction and the magnitude of themotion of the selector and to transmit an input to the ETS 20 whichtransmits a command input to the TCU 16. The output from the sensormeans 18 is an analogue signal in the form of a voltage Vps that issupplied to an analogue to digital converter 30 the digital output ‘X’from which is supplied to a microprocessor forming part of the ETS 20.

It will be appreciated that, for other arrangements of selector,different selector arrangements will be required.

FIGS. 4A to 4D show respectively, a rotary selector 17 with angularsensor 18, a lever with pivot selector and angular sensor, a slidingselector with a linear sensor and a column selector with pivot angularsensor. In each case the arrow ‘A’ shows the part of the selector movedby the user and the arrow ‘B’ shows the motion detected by the sensor.This invention is equally applicable to any of these sensorarrangements.

The rotary selector 17 is associated with an arrangement of illuminatedlabels (P, R, N, D, S) 19 indicating the selected mode. The selector 17further includes an indexing mechanism 24 for maintaining theimmobilisation of the selector in its different positions respectivelyP, R, N and D but also enabling the driver to perceive the transitionfrom one position to another as illustrated in FIGS. 5 to 7.

In one example, the indexing mechanism 24 comprises a detent plate whichis provided on its periphery with notches over a sector and these can beengaged successively by a spring-loaded detent member or detent pin whenthe detent plate rotates as explained more fully in GB-A-2420833 forinstance.

The selector system 12 further includes a locking device 26 controlledby the transmission control unit 16 via the ETS 20 for preventingmovement of the selector 17 when the selector is in Park position and abrake pedal 15 has not been depressed. In one example, the lockingdevice 26 (not shown in detail) is a solenoid actuator engageable with aslot arranged within the detent plate.

The TCU 16 is also connected to a driver display 23 forming part of aninstrument pack 25 in order to indicate the currently engaged gear ofthe transmission 11.

The indexing mechanism 24 is conformed in such a way as to provide apeak and trough force feedback to the driver. That is to say, when theselector 17 is moved from one stable position to another the forceincreases until it reaches a peak and then reduces again to the nextstable position.

When the indexing mechanism 24 becomes worn or dirty due to use there isa possibility that that the selector 17 can be left in an intermediateor peak force position.

In the case of a prior art system this has the risk that the selector 17might be unintentionally moved from a non drive position, i.e. Park orNeutral to a drive position, i.e. Reverse or Drive by a subsequentvibration, shock or even unintentionally by a person and thus shiftingthe transmission into one of the driving positions. It will beappreciated that when in a non-drive position a driver may decide toleave the vehicle or could blip the throttle expecting no movement ofthe vehicle 1.

By way of example, and as shown in FIG. 5, if the selector 17 is left inthe position ‘A’ then it can fall into either of the positions ‘B’ or‘C’, if it falls to position ‘B’ then a safe result is achieved but ifit falls to position ‘C’ an unsafe result is achieved because it hasmoved from a non-drive mode (park) into a drive mode (reverse).Similarly, if the selector 17 is left in the position ‘D’ then it canfall into either of the positions ‘E’ or ‘C’, if it falls to position‘E’ then a safe result is achieved but if it falls to position ‘C’ anunsafe result is achieved because it has moved from a non-drive mode(neutral) into a drive mode (reverse). This is the problem which theinvention set forth herein in solves.

It will be appreciated by those skilled in the art that although theforce feedback is shown in FIGS. 5 to 7 for ease of understanding as asharp peaked zigzag force response with linear changes in between peaksand troughs, this need not be the case and the force may varynon-linearly between the peaks and troughs and the peaks and troughs maybe curvilinear such as would be the case if the force varied in the wayof a sinusoidal output.

Referring now to FIGS. 6 and 8 operation of a first embodiment of theinvention will be described.

The apparatus is as previously described but in this case the ETS 20 isarranged to calibrate the output from the sensor 18 such that each ofthe peak force positions 200, 500, 800 and 1100 corresponds to a drivemode position and so even if the selector 17 is left at one of the peakpositions and then falls to one of the trough or stable positions 50,350, 650, 950 and 1250 a safe outcome is produced.

For example if the selector 17 is left at the peak force position 200 adrive mode namely reverse is already selected and so if the selector 17falls back to stable position 50 a safe outcome results in that thetransmission is transferred from a drive mode to a non-drive mode namelypark. If the selector 17 falls forward to stable position 350 a safeoutcome results in that the transmission remains in the reverse drivemode.

Similarly, if the selector 17 is left at the peak force position 500 adrive mode namely reverse is already selected and so if the selector 17falls back to stable position 350 a safe outcome results in that thetransmission remains in the reverse drive mode and, if the selector 17falls forward to stable position 650, a safe outcome results in that thetransmission is transferred from the reverse drive mode to a non-drivemode namely neutral.

To achieve this result the ETS 20 is programmed so as to divide theoutput range of the at least one sensor 18 into a number of bands havingupper and lower limits corresponding to the various operating modes.

The digital output from the analogue converter 30 ranges in this examplefrom 0 to 1300 for the full range of movement of the selector 17. Thebands set up by the ETS are in this example 0 to 175 for park, 175 to525 for reverse, 525 to 750 for neutral, 750 to 1100 for drive and 1100to 1300 for sport. It will be appreciated that the selector 17 isoperable to reversibly select the operating modes in the sequence park,reverse, neutral, drive and sport.

The bands are arranged such that, when the selector 17 is located at anyone of the peak force feedback positions 200, 500, 800 and 1100 themagnitude of signal output from the at least one sensor 18 falls withinone of the drive mode bands reverse, drive or sport. Note that 200, 500,800 and 1100 are the digital magnitudes corresponding to the peak forcepositions.

Referring now to FIG. 8 there is shown the method used by the ETS 20 todetermine the operating mode of the transmission 11.

Starting at block 5 a key-on state is determined, then at block 20 theETS 20 determines whether the digital output ‘X’ from the analogue todigital converter 30 is less than 175, if it is, then park mode isselected as indicated by block 25 and the method returns via block 5 toblock 20 unless the key-on test at 5 is failed, in which case, themethod ends at 100. Note that in all cases, the required operating modeis selected by the ETS 20 commanding the TCU 16 to select theappropriate operating mode.

If at block 20 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 175 then the methodadvances to block 30 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 175 butless than 525, if it is, then reverse mode is selected as indicated byblock 35 and the method returns via block 5 to block 20 unless thekey-on test at 5 is failed, in which case, the method ends at 100.

Note that the test at block 30 could alternatively be (Is X<525) becauseto reach block 30 it is known than X must be greater than 175.

If at block 30 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 525 then the methodadvances to block 40 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 525 butless than 750, if it is, then neutral mode is selected as indicated byblock 45 and the method returns via block 5 to block 20 unless thekey-on test at 5 is failed, in which case, the method ends at 100.

Note that the test at block 40 could alternatively be (Is X<750) becauseto reach block 40 it is known than X must be greater than 525.

If at block 40 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 750 then the methodadvances to block 50 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 750 butless than 1100, if it is, then drive mode is selected as indicated byblock 55 and the method returns via block 5 to block 20 unless thekey-on test at 5 is failed, in which case, the method ends at 100.

Note that the test at block 50 could alternatively be (Is X<1100)because to reach block 50 it is known than X must be greater than 750.

If at block 50 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 1100 then the methodadvances to block 60 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 1100, ifit is, then sport mode is selected as indicated by block 65 and themethod returns via block 5 to block 20 unless the key-on test at 5 isfailed, in which case, the method ends at 100. If the test at block 60is failed the method returns via block 5 to block 20.

It will be appreciated that the tests indicated in blocks 20 to 60 couldbe performed simultaneously whereas the alternative tests indicatedabove need to be performed in the sequence shown.

Therefore, if the selector 17 is located at the position 200, from block30 reverse drive will be selected because 200 lies in the range 175 to525.

If the selector 17 falls back to the stable position 50 the test atblock 20 will be passed because 50 is less than 175 and the transmission11 will be placed in a safe non-drive mode namely park and if theselector 17 falls forward from the peak position 200 to the stableposition 350 the test at 30 will be passed because 350 lies in the range175 to 525 and the transmission 11 will be remain in the same drive modenamely reverse. In either case a safe result is achieved.

Similarly, if the selector 17 is located at the position 500 from block30 reverse drive will be selected because 500 lies in the range 175 to525.

If the selector 17 falls back from 500 to the stable position 350 thetest at block 30 will be passed because 350 lies in the range 175 to 525and the transmission 11 will remain in the same drive mode namelyreverse and if the selector 17 falls forward from the peak position 500to the stable position 650 the test at 40 will be passed because 650lies in the range 525 to 750 and the transmission 11 will be placed in asafe non-drive mode namely neutral. In either case a safe result isachieved.

Referring now to FIGS. 7 and 9 there is shown a second embodiment of theinvention.

The apparatus is as previously described and the ETS 20 is arranged tocalibrate the output from the sensor 18 such that each of the peak forcepositions 200, 500, 800 and 1100 corresponds to a drive mode positionand so even if the selector 17 is left at one of the peak positions andthen falls to one of the trough or stable positions 50, 350, 650, 950and 1250 a safe outcome is produced.

As before, if the selector 17 is left at the peak force position 200, adrive mode namely reverse is already selected and so if the selector 17falls back to stable position 50 a safe outcome results in that thetransmission is transferred from a drive mode to a non-drive mode namelypark. If the selector 17 falls forward to stable position 350 a safeoutcome results in that the transmission remains in the reverse drivemode. Similarly, if the selector 17 is left at the peak force position500 a drive mode namely reverse is already selected and so if theselector 17 falls back to stable position 350 a safe outcome results inthat the transmission remains in the reverse drive mode and, if theselector 17 falls forward to stable position 650, a safe outcome resultsin that the transmission is transferred from the reverse drive mode to anon-drive mode namely neutral.

To achieve this result the ETS 20 is programmed so as to divide theoutput range of the at least one sensor 18 into a number of bands havingupper and lower limits corresponding to the various operating modes butin the case of this embodiment the upper and lower limits of these bandsare different depending upon the direction in which the selector 17 ismoved.

As before, the digital output ‘X’ from the analogue converter 30 rangesfrom 0 to 1300 for the full range of movement of the selector 17.

The bands set up by the ETS 20 when the selector is being moved frompark to reverse, reverse to neutral and neutral to drive are 0 to 180for park, 180 to 550 for reverse, 550 to 770 for neutral, 770 to 1150for drive and 1150 to 1300 for sport.

When the selector 17 is being moved from sport to drive, drive toneutral, neutral to reverse and reverse to park are 0 to 160 for park,160 to 540 for reverse, 540 to 750 for neutral, 750 to 1050 for driveand 1050 to 1300 for sport.

It will be appreciated that the selector 17 is operable to reversiblyselect the operating modes in the sequence park, reverse, neutral, driveand sport.

The difference in these upper and lower limits is to reduce unstableoperation of the transmission and reduce unnecessary operating modechanges.

These bands are arranged such that, when the selector 17 is located atany one of the peak force feedback positions 200, 500, 800 and 1100 themagnitude of signal output from the at least one sensor 18 falls withinone of the drive mode bands reverse, drive or sport. Note that 200, 500,800 and 1100 are the digital magnitudes corresponding to the peak forcepositions.

It will be noted that the upper and lower limits are higher when theselector 17 is moved from one of park to reverse, reverse to neutral andneutral to drive than they are when the selector 17 is moved from one ofdrive to neutral, neutral to reverse and reverse to park.

Referring now to FIG. 9 there is shown the method used by the ETS 20 todetermine the operating mode of the transmission 11.

Starting at block 105 a key-on state is determined, the ETS 20 then atblock 110 determines the direction of displacement of the selector 17 bycomparing the current output Xnew from the analogue to digital converter30 with a previous value Xold. If Xnew is greater than Xold the methodadvances to block 120 other wise it advances to block 220. That is tosay, if the direction of movement is from park towards sport or anyintermediate positions, the blocks 120 to 160 are performed but if theselector 17 is being moved from the sport position or any intermediateposition towards the park position the blocks 220 to 260 are performed.

Considering first the passing of the test at step 110 then at block 120the ETS 20 determines whether the digital output ‘X’ from the analogueto digital converter 30 is less than 180, if it is, then park mode isselected as indicated by block 300 and the method returns via block 105to block 110 unless the key-on test at 105 is failed, in which case, themethod ends at 900. Note that in all cases, the required operating modeis selected by the ETS 20 commanding the TCU 16 to select theappropriate operating mode.

If at block 120 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 180 then the methodadvances to block 130 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 180 butless than 550, if it is, then reverse mode is selected as indicated byblock 400 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 130 could alternatively be (Is X<550)because to reach block 30 it is known than X must be greater than 180.

If at block 130 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 550 then the methodadvances to block 140 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 550 butless than 770, if it is, then neutral mode is selected as indicated byblock 500 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 140 could alternatively be (Is X<770)because to reach block 140 it is known than X must be greater than 550.

If at block 140 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 770 then the methodadvances to block 150 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 770 butless than 1150, if it is, then drive mode is selected as indicated byblock 600 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 150 could alternatively be (Is X<1150)because to reach block 150 it is known than X must be greater than 770.

If at block 150 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 1150 then the methodadvances to block 160 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 1150, ifit is, then sport mode is selected as indicated by block 700 and themethod returns via block 105 to block 110 unless the key-on test at 105is failed, in which case, the method ends at 900. If the test at block160 is failed the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

It will be appreciated that the tests indicated in blocks 120 to 160could be performed simultaneously whereas the alternative testsindicated above need to be performed in the sequence shown.

Therefore as previously described, if the selector 17 is located at theposition 200 from block 130 reverse drive will be selected because 200lies in the range 180 to 550.

If the selector 17 falls back to the stable position 50 the test atblock 120 will be passed because 50 is less than 180 and thetransmission 11 will be placed in a safe non-drive mode namely park andif the selector 17 falls forward from the peak position 200 to thestable position 350 the test at 130 will be passed because 350 lies inthe range 180 to 550 and the transmission 11 will remain in the samedrive mode namely reverse. In either case a safe result is achieved.

Similarly, if the selector 17 is located at the position 500 from block130 reverse drive will be selected because 500 lies in the range 180 to550.

If the selector 17 falls back from 500 to the stable position 350 thetest at block 130 will be passed because 350 lies in the range 180 to550 and the transmission 11 will remain in the same drive mode namelyreverse and if the selector 17 falls forward from the peak position 500to the stable position 650 the test at 140 will be passed because 650lies in the range 550 to 770 and the transmission 11 will be placed in asafe non-drive mode namely neutral. In either case a safe result isachieved.

Considering now the failing of the test at step 110 then at block 220the ETS 20 determines whether the digital output ‘X’ from the analogueto digital converter 30 is less than 160, if it is, then park mode isselected as indicated by block 300 and the method returns via block 105to block 110 unless the key-on test at 105 is failed, in which case, themethod ends at 900.

If at block 220 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 160 then the methodadvances to block 230 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 160 butless than 530, if it is, then reverse mode is selected as indicated byblock 400 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 230 could alternatively be (Is X<530)because to reach block 230 it is known than X must be greater than 160.

If at block 230 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 530 then the methodadvances to block 240 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 530 butless than 750, if it is, then neutral mode is selected as indicated byblock 500 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 240 could alternatively be (Is X<770)because to reach block 240 it is known than X must be greater than 530.

If at block 240 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 750 then the methodadvances to block 250 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 750 butless than 1050, if it is, then drive mode is selected as indicated byblock 600 and the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

Note that the test at block 250 could alternatively be (Is X<1050)because to reach block 150 it is known than X must be greater than 750.

If at block 250 the digital output ‘X’ from the analogue to digitalconverter 30 is determine to be greater than 1050 then the methodadvances to block 260 where it is determined whether the digital output‘X’ from the analogue to digital converter 30 is greater than 1050, ifit is, then sport mode is selected as indicated by block 700 and themethod returns via block 105 to block 110 unless the key-on test at 105is failed, in which case, the method ends at 900. If the test at block260 is failed the method returns via block 105 to block 110 unless thekey-on test at 105 is failed, in which case, the method ends at 900.

It will be appreciated that the tests indicated in blocks 220 to 260could be performed simultaneously whereas the alternative testsindicated above need to be performed in the sequence shown.

Therefore as previously described, if the selector 17 is located at theposition 200 from block 230 reverse drive will be selected because 200lies in the range 160 to 530.

If the selector 17 falls back to the stable position 50 the test atblock 220 will be passed because 50 is less than 160 and thetransmission 11 will be placed in a safe non-drive mode namely park andif the selector 17 falls forward from the peak position 200 to thestable position 350 the test at 230 will be passed because 350 lies inthe range 160 to 530 and the transmission 11 will be remain in the samedrive mode namely reverse. In either case, a safe result is achieved.

Similarly, if the selector 17 is located at the position 500 from block230 reverse drive will be selected because 500 lies in the range 160 to530.

If the selector 17 falls back from 500 to the stable position 350 thetest at block 230 will be passed because 350 lies in the range 160 to530 and the transmission 11 will remain in the same drive mode namelyreverse and if the selector 17 falls forward from the peak position 500to the stable position 650 the test at 240 will be passed because 650lies in the range 530 to 750 and the transmission 11 will be placed in asafe non-drive mode namely neutral. In either case a safe result isachieved.

Therefore in summary, a driver of a motor vehicle fitted with a controlapparatus according to the invention cannot produce an unsafe conditionin which the driver believes the transmission is in a safe non-drivemode but is in fact balanced between two modes and can fall into anunsafe drive mode which may result in unintended movement of the motorvehicle. In all cases either a drive mode will be maintained or thetransmission will fall into a safe non-drive mode. It will beappreciated that a driver knowing that a drive mode is selected isunlikely to leave the motor vehicle or blip the throttle.

Although the invention has been described with reference to a rotaryselector using only one sensor it will be appreciated that it is equallyapplicable to selector mechanisms having more than one sensor feedbackor selectors of a linear type.

The invention claimed is:
 1. An apparatus for controlling a motorvehicle transmission, the transmission having a number of operatingmodes including at least one non-drive mode and at least one drive mode,the apparatus comprising: a multi-stable shift-by-wire rotary selectorfor operation by a driver to select a respective one of the operatingmodes of the transmission; at least one sensor for sensing a position ofthe multi-stable shift-by-wire rotary selector in a range of possiblepositions and configured to output a signal indicative of the position;an electronic controller configured to receive the signal from the atleast one sensor and select one of the number of operating modes basedupon the signal; wherein the multi-stable shift-by-wire rotary selectorincludes a mechanism configured to provide a number of stable positionscorresponding to the number of operating modes with each stable positionrepresenting a specific operating mode, the mechanism further configuredto provide a peak and trough force feedback that enables driverperception of a transition from one stable position to another stableposition; and wherein the electronic controller is operable to dividethe range of the at least one sensor into a number of bands having upperand lower limits, the bands corresponding respectively to the number ofoperating modes, and to arrange the number of bands such that, when themulti-stable shift-by-wire rotary selector is located at any one of thestable positions, the position of the multi-stable shift-by-wire rotaryselector represented by the signal from the at least one sensor fallswithin a respective one of the bands, the upper and lower limits of eachband that occur between operating modes being different depending on adirection of movement of the multi-stable shift-by-wire rotary selector.2. An apparatus as claimed in claim 1, wherein the number of operatingmodes comprises two non-drive modes in the form of a park mode and aneutral mode and two drive modes in the form of a reverse mode and aforward mode.
 3. An apparatus as claimed in claim 2, wherein themulti-stable shift-by-wire rotary selector is operable to reversiblyselect the operating modes in a sequence of the park mode, the reversemode, the neutral mode and the forward mode.
 4. An apparatus as claimedin claim 2, wherein the number of operating modes further comprise athird drive mode in the form of a sport mode.
 5. An apparatus as claimedin claim 4, wherein the multi-stable shift-by-wire rotary selector isoperable to reversibly select the operating modes in a sequence of thepark mode, the reverse mode, the neutral mode, the forward mode and thesport mode.
 6. An apparatus as claimed in claim 1, wherein theelectronic controller is further operable to arrange the number of bandssuch that, when the multi-stable shift-by-wire rotary selector islocated at any one of the peak force feedback positions, the position ofthe multi-stable shift-by-wire rotary selector represented by the signaloutput from the at least one sensor falls within any one of the bandsthat correspond to a drive mode.
 7. An apparatus as claimed in claim 1,wherein the upper and lower limits of each band are higher when themulti-stable shift-by-wire rotary selector is moved in one directionthan they are when the multi-stable shift-by-wire rotary selector ismoved in an opposite direction.
 8. An apparatus as claimed in claim 7,wherein the at least one non-drive mode of the number of operating modesincludes a park mode and a neutral mode, and the at least one drive modeof the number of operating modes includes a reverse mode and a forwardmode, and wherein the upper and lower limits are higher when themulti-stable shift-by-wire rotary selector is moved from one of the parkmode to the reverse mode, the reverse mode to the neutral mode and theneutral mode to the forward mode than they are when the multi-stableshift-by-wire rotary selector is moved from one of the forward mode tothe neutral mode, the neutral mode to the reverse mode and the reversemode to the park mode.
 9. An apparatus as claimed in claim 7, whereinthe at least one non-drive mode of the number of operating modesincludes a park mode and a neutral mode, and the at least one drive modeof the number of operating modes includes a reverse mode and a forwardmode, the number of operating modes further including a third drive modein the form of a sport mode, and wherein the upper and lower limits arehigher when the multi-stable shift-by-wire rotary selector is moved fromone of the park mode to the reverse mode, the reverse mode to theneutral mode, the neutral mode to the forward mode and the forward modeto the sport mode than they are when the multi-stable shift-by-wirerotary selector is moved from one of the sport mode to the forward mode,the forward mode to the neutral mode, the neutral mode to the reversemode and the reverse mode to the park mode.
 10. An apparatus as claimedin claim 1, wherein the electronic controller comprises an electronictransmission selector operably connected to a transmission control unitand the electronic transmission selector is operable to receive thesignal from the at least one sensor and command the transmission controlunit to select a desired operating mode.
 11. An apparatus as claimed inclaim 10, wherein the electronic transmission selector is connected tothe transmission control unit via a CAN bus.
 12. An apparatus as claimedin claim 1, wherein a magnitude of the signal output from the at leastone sensor corresponds to a specific position of the multi-stableshift-by-wire rotary selector.
 13. An apparatus as claimed in claim 12,wherein the electronic controller is further configured to store a valueof the magnitude of the signal and to determine a direction of rotationof the multi-stable shift-by-wire rotary selector in dependence on acomparison between a currently measured magnitude of the signal outputfrom the at least one sensor and a previously stored value.
 14. Anapparatus as claimed in claim 1, wherein the mechanism includes a detentplate.
 15. An apparatus for controlling a motor vehicle transmission,the transmission having a number of operating modes including at leastone non-drive mode and at least one drive mode, the apparatuscomprising: a multi-stable shift-by-wire rotary selector for operationby a driver to select a respective one of the operating modes of thetransmission; at least one sensor for sensing a position of themulti-stable shift-by-wire rotary selector in a range of possiblepositions of the multi-stable shift-by-wire rotary selector andconfigured to output a signal indicative of the position; and anelectronic controller configured to receive the signal from the at leastone sensor and select one of the number of operating modes based uponthe signal; wherein the multi-stable shift-by-wire rotary selectorincludes a mechanism configured to provide a number of stable positionscorresponding to the number of operating modes with each stable positionrepresenting a specific operating mode, the mechanism further configuredto provide a peak and trough force feedback so as to enable driverperception of a transition from one stable position to another stableposition; wherein the electronic controller is operable to divide therange of possible positions of the multi-stable shift-by-wire rotaryselector into a number of bands having upper and lower limitscorresponding to the number of operating modes and arrange the bandssuch that, when the multi-stable shift-by-wire rotary selector islocated at any one of the stable positions, the position of themulti-stable shift-by-wire rotary selector represented by the signalfrom the at least one sensor falls within a respective one of the bands,the upper and lower limits of each band that occur between operatingmodes being different depending on a direction of movement of themulti-stable shift-by-wire rotary selector.
 16. An apparatus as claimedin claim 15, wherein the electronic controller is further operable toarrange the bands such that, when the multi-stable shift-by-wire rotaryselector is located at any one of the peak force feedback positions, theposition of the multi-stable shift-by-wire rotary selector representedby the signal from the at least one sensor falls within one of the bandscorresponding to drive mode.
 17. An apparatus as claimed in claim 15,wherein the upper and lower limits of each band that occur betweenoperating modes are higher when the multi-stable shift-by-wire rotaryselector is moved in one direction than they are when the multi-stableshift-by-wire rotary selector is moved in an opposite direction.
 18. Anapparatus as claimed in claim 17, wherein the number of operating modesincludes park, reverse, neutral and drive, and wherein the upper andlower limits are higher when the multi-stable shift-by-wire rotaryselector is moved from one of park to reverse, reverse to neutral andneutral to drive than they are when the multi-stable shift-by-wirerotary selector is moved from one of drive to neutral, neutral toreverse and reverse to park.
 19. An apparatus as claimed in claim 18,wherein the number of operating modes further includes sport, andwherein the upper and lower limits are higher when the multi-stableshift-by-wire rotary selector is moved from one of park to reverse,reverse to neutral, neutral to drive and drive to sport than they arewhen the multi-stable shift-by-wire rotary selector is moved from one ofsport to drive, drive to neutral, neutral to reverse and reverse topark.
 20. A motor vehicle, comprising: a transmission having a number ofoperating modes including at least one non-drive mode and at least onedrive mode; and an apparatus for controlling the transmission, theapparatus including: a multi-stable shift-by-wire rotary selector foroperation by an occupant to select a respective one of the operatingmodes of the transmission; at least one sensor for sensing a position ofthe multi-stable shift-by-wire rotary selector in a range of possiblepositions of the multi-stable shift-by-wire rotary selector andconfigured to output a signal indicative of the position; an electroniccontroller configured to receive the signal from the at least one sensorand select one of the number of operating modes based upon the signal;wherein the multi-stable shift-by-wire rotary selector includes amechanism configured to provide a number of stable positionscorresponding to the number of operating modes with each stable positionrepresenting a specific operating mode, the mechanism further configuredto provide a peak and trough force feedback that enables driverperception of a transition from one stable position to another stableposition; wherein the electronic controller is operable to divide therange of possible positions of the multi-stable shift-by-wire rotaryselector into a number of bands each having an upper and lower limit,each of the number of bands corresponding to a respective one of thenumber of operating modes, the electronic controller further operable toarrange the number of bands such that the position of the multi-stableshift-by-wire rotary selector represented by the signal from the atleast one sensor falls within a respective one of the number of bandswhen the multi-stable shift-by-wire rotary selector is located at anyone of the number of stable positions; and wherein the upper and lowerlimit of each band that occurs between operating modes is differentdepending on a direction of movement of the multi-stable shift-by-wirerotary selector.